Vapor compression still with distilland recirculation means



C. R. SPERRY VAPOR COMPRESSION STILL WITH DISTILLAND RECIRCULATION MEANS Filed July 3l, 1967 5 Sheets-Sheet l Dec. 30, 1969 c. R. SPERRY 3,486,984

VAPOR COMPRESSION STILL WITH DISTILLAND REGIRGULATION MEANS Iaweiaba'f: wie@ R. 5.2212242435 Dec. 30, 1969 C, R, s-PERRY 3,486,984

VAPOR coMPREssIoN STILL WITH DISTILLAND RECIRGULATION MEANS Filed July 3l, 1967 5 Sheets-Sheet 5 www qjefllllllllyl ll Dec. 30, 1969 c. R. sPERRY A 3,436,984

VAPOR COMPRESSION STILL WITH DISTILLAND RECIRCULATION MEANS Filed July 31, 1967 5 Sheets-Sheet 4 Dec. 30, 1969 l C. R. SPERRY VAPOR COMPRESSION STILL WITH DISTILLAND RECIRCULATION MEANS Filed July 31, 196'7 5 Sheets-Sheet 5 calm/IM@ United States Patent O 3,486,984 VAPOR COMPRESSION STILL WITH DISTILLAND RECIRCULATION MEANS Charles R. Sperry, 28 Church St., Cambridge, Mass. 02138 Filed July 31, 1967, Ser. No. 657,204

' Int. Cl. B01d 3/04, 3/02 U.S. Cl. 202-172 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The present invention relates to a means for distilling fluids in a vapor compression still. It has been theorized in the fractional distillation art that there are four fundamental requirements for maximum eiiiciency in vaporizing and condensing materials which are ordinarily liquid at room temperature. These include rst, that the heat exchange surface ordinarily used in distillation work should comprise a metallic and molecularly clean surface. Secondly, the torpidity of the distilland should be minimized. Thus, it is desirable to minimize the impurities in a distilland which frequently gather as a very thin film of islands on the surface of a boiling or vaporizing distilland and thus reduce considerably the eiciency of vaporization. Third, maximum contact between the distilland and the heat exchange surface should be effected by eliminating or minimizing the size of bubbles on the surface of the heat exchanger and by effecting pressure on the distilland v against the heat exchange surface. Finally, there is a requirement that the depth of the distilland be minimized for greatest efficiency. The earlier attempts to obtain these objectives and thereby maximize the efficiency of distillation has not met with any particular success although a large number of different mechanisms have been designed. These mechanisms are quite frequently sophisticated, cumbersome, ineicient, require considerable maintenance, and interruption of operation, -do not run at initial starting eiciency over a period of time, are expensive to build and maintain, bulky in size and are not reliable at all times. Because of these deliciencies there has been a con' tinuing need for an improved still particularly adapted for distilling water on a continuous basis.

SUMMARY OF INVENTION It is therefore an object of the present invention to provide an improved Vapor compression still which attains many of the objectives enumerated above, including at least the first three set forth.

In the present invention there is provided an arrangement which includes a first and second chamber with the iirst chamber positioned within the second and adapted to contain a distilland continuously fed into it under "ice vacuum conditions. The second chamber is adapted to receive a distillate under pressure from the rst. Means are provided lfor continuously drawing the distilland from the first chamber, continuously vaporizing the distilland and pumping the vapors into the second chamber, whereby pressure is built up in the second chamber While the vapors come in contact with a thin heat conducting Wall separating the two chambers. The increased pressure in the second chamber effects a dew point which condenses the vapors and forms a distillate.

In the present invention there is provided means for continuously feeding distilland against the heat exchange means consisting of a heat conductive wall, with the distilland being fed in such a manner as to continuously effect a cleaning action on the surface of the heat exchange wall. Means are also provided for continuously moving the distilland over the heat exchange surface, thereby minimizing torpidity by taking up and removing the islands of torpidity from the surface of the distilland. The distilland, moreover, is introduced into contact with the surface of the heat exchange Wall at high contact pressures of at least several pounds per square inch, thereby continuously maintaining a good contact between the distilland and heat exchange surface and thereby minimizing the size and number of bubbles which may be formed on the heat exchange surface during vaporization of the distilland. A further object of the present invention is to provide a means for introducing a continuous flow of distilland into a still in a self regulated and controlled fashion so as to eliminate the need for personal supervision and control of the distilland ow. A further object of the present invention is to provide a means for blowdown or removal of excess impurities, thereby maintaining an impurity level in the distilland at a controlled and at a substantially constant iigure. This in turn eliminates the need for skilled personnel ordinarily required in the maintenace of stills of earlier design.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of the present invention may be more clearly understood when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a vertical cross sectional elevation of the still embodying the present invention;

. FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1;.

FIG. 3 is a cross sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a cross sectional view taken along the line 4-4 of FIG. 1;

FIG. 5 is a vertical cross sectional detail taken substantially along the line A5--5 of FIG. 4;

FIG. 6y is a cross sectional view taken substantially along line 6-6 of FIG. 1;

FIG. 7 is a cross sectional view taken along line 7-7 of FIG. 6; and

FIG. 8 is a cross sectional elevation of a modification of the invention showing a bank of vacuum compression extractors in a single insulated still casing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be described primarily in conjunction with a single embodiment illustrated in FIGS. 1 to 7 inclusive. However, it is understood that the invention is not to be limited by the embodiments specifically described.

Referring to FIGS. l through 7 there is illustrated a vacuum compression extractor generally indicated at 1 and an insulated still casing generally illustrated at 2. The insulated still casing 2 comprises a continuous side wall 3 and integral bottom 4 which is open at its upper end 5. The continuous sidewall 3 and bottom 4 may be formed of an outer lamination of outer insulating material 5, such as a ceramic or the like and an inner wall or 6 of metal, such as stainless steel.

An outlet valve or tap 7 is provided at a low point for periodically tapping the distallate 8 which is collected at the bottom of the still casing. The upper end of the still casing 2 may be provided with a shoulder 9 adapted to receive and secure the upper end of the vacuum compression extractor 1 which fits in and is secured to the casing 2.

The vacuum compression extractor 1 consists primarily of four major components including a molded plastic housing 10, the compound vacuum rotor 11, the centrifugal pump 12 and a heat exchange cone 13. The housing is provided with an upper periphery 15 adapted to tit over and be secured to the upper edge of the still casing 3 by means of a series of screws 16. This housing 10 is provided with an opening through which a distilland or inlet tube 17 extends. This tube 17 may be suitably connected to any source of supply of the distilland which may be constantly metered into the still. The lower end of this inlet tube 17 extends through the housing 10 and is positioned immediately above the upper portion of the inner surface of the cone 13. An outlet tube 18 also extends through the housing 10. The other end is adapted to carry excess distilland from the unit and may be connected to a suita-ble reciving device. The lower end of the outlet tube is positioned within and at the upper end of the cone 13 against the inner surface of the cone wall. The diameter of tube 18 is critical and is sized relative to the diameter of tube 17 such as to maintain a constant volume of distilland in cone 13 and provide a constant blow down, The depth of the distilland which is built up on the inner surface of the cone wall 13 is thus maintained constant. Further, the impurities collecting within cone 13 migrate toward the upper end of the cone 13 during the operation of the unit, as hereafter described, and are then removed through tube 18. The lower surface of the housing 10 is provided with a recess or inverted Well 20 which is adapted to receive the centrifugal pump assembly 12, hereafter described. Extending radially from this well 20 are a plurality of passages 21 which interconnect the Well 20 with the chamber 23 formed between the still casing 2 and the vacuum compressor extractor 1. The well 20 in turn is connected to the chamber 24 formed within the cone 13 thereby providing a means for moving vapors from chamber 24 to the well 20, passages 21 and into the chamber 23 in a manner hereafter described.

The lower surface of the housing 10 is provided with an annular shoulder section 25 to which the upper edge of the cone 13 is secured. The upper edge of the cone is provided with an outwardly liared flange 26 through which a series of screws 27 extend thereby securing the cone 13 to the housing 10. A series of O-ring seals'28 or other suitable sealing means effects a permanent watertight seal between the housing 10 and the cone 13. The cone 13 is formed of a thin metal preferably highly polished and may, for example, comprise stainless steel. The cone is preferably substantially frustoconical in shape, having a continuous bottom 30 which extends downwardly toward and close to the bottom Wall 4 of the casing 2.

The housing 10 which functions as a cover for the still also provides insulation for the electrical wire which extends through the housing 10 to the motor 36 of the centrifugal pump 12. The centrifugal pump 12 comprises the pump motor 36 connected by shaft 37 to the centrifugal pump rotor 38. The motor 36 and shaft 37 are mounted in a common casing 39 in turn suitably secured to a base 40 with this base at the upper end of the centrifugal pump assembly and secured to a shoulder in the well 20 of the housing by a series of screws 41 at the periphery of this base. This lbase 40 is provided with passages 42 which extend radially from the axis of the casing and are connected at their outer ends and open into chamber 24 at 43. The inner end of these passages 42 open into the interior of the well 20. (FIG. 6). The shaft 37 of motor 36 also extends upwardly into the Well 20 and has mounted on it a series of rotors 45, 46 within the well 20, with vanes adapted to move vapors outwardly from the axis. These rotors 45, 46 may be suitably interposed with stators 47 formed or secured to the inner wall of the well 20. The shaft 30 may also be provided with a perforated spacer 50 having a plurality of apertures 51 through which vapors from passage 42 may move into the well 20.

Surrounding the common casing 39 which encloses the motor 36 and shaft 37 is an outer casing 55. The upper end of the cylindrical outer casing 55 is connected to the common casing 39 by threads 56 to form a space 58, closed at the top by the threads 56 but with the bottom 59 of this space connected to the interior 60 of a hollow dip tube 61. The dip tube 61 is integrally connected to the shell 55 by flange member 64. A tube 66 interconnects the space 58 between the casing 39 and outer casing 55 with chamber 24. This tube 66 is tangentially arranged with respect to the inner surface of cone 13 so as to project water against the cones inner surface near its top with a circulating or swirling motion. Thus distilland moving up the tube 61 is forced by the pump rotor 38 about the casing 39 in space 58 and outwardly through outer casing 55 through the tube 66.

The bottom of the tube 61 is provided with a fixture 70 best illustrated in FIGS. 4 and 5. In this arrangement the lower end of the dip tube 61 is open. Fitted within this open end is the fixture 70 which is designed to break up a vortex'and to prevent or minimize air from being entrained in the distilland and moving up the dip tube 61. In this arrangement there is provided a valve 71 and a valve seat 72 suitably formed in a tting element 73. A passage 74 through the fitting 73 is normally closed by the weight of the valve 71. The valve 71 may, however, be moved upwardly to open this opening 74 under the pressure of upwardly moving distilland. The upward movement of valve 71 is guided by the shaft 75 connected to its lower end and journaled for vertical movement in the bridge 77. A cotter pin 78 limits the upward movement of the valve by engagement of the pin with the lower end of the bridge 77. A series of bafe elements 79 supported on and integrally formed With a ring 80 extend radially outward from the lower end of the outer surface of the dip tube 71 with these baffles 79 adapted to break up the distilland as it passes into the dip tube 61. The ring 80 may be force fit or other- Wise suitably secured at the lower end of the dip tube 61.

In the operation of this still the distilland which may, for example, comprise salt or ocean water loaded with sand or other particulate matter for cleaning purposes is introduced into the chamber 24 and the motor 36 is turned on.

The rotation of the motor 36 causes the rotor 38 to rotate thus drawing the distilland up through the dip tube 61. The distilland is drawn through the space 58 deiined by the casing 39 and outer casing 55 and is forced outwardly through tube 66 at a Very high velocity and in substantial volume. The distilland is thus emitted tangentially at the top of the heat exchange cone at a rate sufficient to provide a whirling action which spreads the distilland with reasonably even thickness onto the walls of the cone 13. This whirlpool action produces increased pressure on the cone producing a constant agitation and also producing a scrubbing action which maintains the walls of the cone continuously clean and shiney.

As described herein, the high speed of the moving distilland over the surface of the cone means speeds in the order of magnitude of 500 r.p.m. to 10,000 r.p.m. While somewhat lower speeds, e.g., 100 r.p.m. to 500 r.p.m., may be operational, operations at such speeds will not be efficient. A continuous input of distilland may be introduced through the tube 17 with the distilland containing more sand or other particulate matter which will aid in the scrubbing and cleaning action of the interior surface of the cone 13 is desired. The motor, in addition to functioning as a source for operating the centrifugal pump also provides the necessary heat for purposes of starting and maintaining the distillation cycle. This, incidentally, eliminates the need for a secondary heat supply and the pertinent controls which would otherwise be required. As the motor 36 continues to operate, its heat causes vaporization of the distilland 80 (in this case water) at a temperature of approximately 200 F. within the chamber 24.

As this motor operates it gets hot and in turn generates sufficient heat to heat the distilland 80. As the distilland 80 becomes hotter it vaporizes as illustrated-at 81. If the distilland is ocean water it starts to vaporize at about 200 F., and quantities of it start moving through the passages 42 where it is picked up by the rotating vanes of the rotors 45, 46 and is driven outwardly through the passages 21 into chamber 23. As the unit continues to operate, the vapor pressure in chamber 23 increases as does the pressure within the chamber or well 30.

The pure vapor now within the chamber 23 is superheated by the compressive action of the pump and thus pressure is maintained within chamber 23. The vapor in chamber 23 comes into contact with the outer surface of the cone wall 13 and because of its increased temperature and pressure creates a dew point situation and thereby condenses on the outer wall of the cone. This condensation runs off the cone to the bottom of the casing 2 and collects in a pool 8. The heat transfer by which the vapor condenses imparts heat to the cone wall 13 which heat is transferred through the cone wall to effect further vaporization of the distilland Within chamber 24, thereby producing Imore vapor.

The cycle described above continues at the same starting efficiencies because the inner surface of the cone 13 is maintained clean at all times by the whirling and purging action of the distilland.

In constructing the unit described it is important to provide a construction which maintains the proper pressures and therefore careful sealing of the various components described must be effected. The distilland side must withstand vacuums while the distillate side must withstand pressures. The critical seal between these pressure areas, namely chamber 24 and chamber 23, comes at the shaft of the |motor 36 which is connected to the centrifugal pump rotor. The problem of effecting this seal at a high r.p.m. in the order of 20,000 is overcome by bleeding a small amount of vapor from the high pressure side of the vacuum pump through the shaft of the motor and into the motor housing. This hot vapor in turn relieves itself through small tolerances of the pump shaft and rotor. When the unit is not working and the motor is at rest, a static seal is effected due to the absence of pressure. This may be attained in two ways. Bleed holes may be drilled in the water jacket to relieve the head depth below the shaft outlet level or the armature may be spring loaded slightly to bring the resting pump rotor up against static Teflon seal.

The depth or level of the distilland is controlled by tube 18 which automatically allows a blowdown of excess distilland thereby effecting a constant control of the depth. Distilland is continuously introduced into the cone through tube 17 at a rate slightly greater than the rate of condensation but equal to the rate of condensation and blowdown. Temperature of the unit may be controlled by a power source to the motor whereby the motor is run at more or less efficient speeds with a heat sensitive valve introduced into the distilland as a feed back type of control for the motor.

The foregoing described invention may be used in conjunction with a variety of processes requiring removal, recondensation, or salvage of vapors which are normally liquid at atmospheric pressures, and processes requiring the separation and salvage in varying environments of solids and/or vapor. The invention also contemplates a variety of modifications including variations in the shape of heat exchange unit and the use of a cylindrical rather than.a conic unit. In addition, a centrifugal pump rotor may be replaced by an air lift pump cycle or other means for similarly raising the distilland, heating it and pumping it from the chamber 24 into chamber 23. However the described embodiment of the invention is believed the most efficient of the preferred embodiments contemplated.

Further, the vacuum compression extractor 1 may be separately embodied in an insulated still casing as illustratedr in FIGS. 1 to 7 or alternately may be combined in a bank of such extractors 1 within a single still casing 5 as illustrated in FIG. 8. In this arrangement the construction of the extractors 1 may be identical to those previously described. The still casing 5 may be modified, if desired, only to the extent of providing a size and arrangement adapted to receive a multiplicity of extractors 1 with the cover 90 of the still casing having a plurality of apertures adapted to receive the plurality of extractors 1.

What is claimed is:

1. A vapor compression still comprising a closed casing, a conical wall within the casing with its wide end above its vertex defining a first and second chamber with the first chamber within the second, said conical wall fixed relative to said casing, said first chamber adapted to contain a distilland under vacuum conditions and said second chamber adapted to receive a distillate under pressure, said conical wall comprising a thin, heat-conductive wall against one side of which said distilland is normally continuously circulated and moved at high speeds over said wall and against the other side of which said vapors may condense, means for continuously circulating said distilland as a whirlpool from the upper end of said first chamber to the lower end thereof comprising a pump at the upper end of said first chamber with means extending to the lower end thereof, and means for continuously drawing said distilland from said first chamber continuously vaporizing said distilland and pumping said vapors into said second chamber.

2. A still as set forth in claim 1 including means for drawing vapor formed within said first chamber and passing it outwardly over said conical wall into said second chamber.

3. A still as set forth in claim 1 wherein said drawing and vaporizing means includes a motor with said pump comprising a centrifugal pump connected to one end of the shaft of said motor, means forming an enclosing chamber about at least a portion of said pump with said portion extending into said first chamber including said means extending to the lower end of said first chamber comprising a dip tube connected to said enclosing chamber about said pump and a tube extending from said enclosing chamber toward the inner surface of said wall for pumping said distilland against the inner surface of said wall.

4. A still as set forth in claim 3 having a rotor connected to said motor and positioned within means form- Y ing a well at the top of said wall with passages extending from said well to said second chamber and from said 7 pump, means for admitting distilland continuously to 2,562,153 7/ 1951 said rst chamber and means for continuously blowing 2,734,023 2/ 1956 down distilland from said rst chamber. 3,282,798 11/ 1966 6. A still as set forth in claim 1 having a plurality of 3,312,600 4/ 1967 means forming said rst chamber Within a single second chamber.

References Cited UNITED STATES PATENTS 2,234,166 3/1941 Hickman 202-236 Taylor 202-236 Hickman 203-26 Tidball 203-26 Morton 202-236 WILBUR L. BASCOMB, I R., Primary Examiner U.S. Cl. X.R. 

